https://leetcode.cn/problems/replace-all-digits-with-characters/description/


class Solution {
public:
    string replaceDigits(string s) {

        for (int i = 0; i < s.size() - 1; i += 2)
        {
            char ch = s[i + 1];
            int num = ch - '0';

            s[i + 1] = s[i] + num;
        }

        return s;
    }
};